On Wed, 1 Feb 2023 13:18:31 GMT, Per Minborg <pminb...@openjdk.org> wrote:
>> `ZoneOffset` instances are cached by the `ZoneOffset` class itself for
>> values in the range [-18h, 18h] for each second that is on an even quarter
>> of an hour (i.e. at most 2*18*4+1 = 145 values).
>>
>> Instead of using a `ConcurrentHashMap` for caching instanced, we could
>> instead use an `AtomicReferenceArray` with direct slot value access for said
>> even seconds. This will improve performance and reduce the number of object
>> even though the backing array will go from an initial 32 in the CHM to an
>> initial/final 145 in the ARA. The CHM will contain much more objects and
>> array slots for typical numbers of entries in the cache and will compute
>> hash/bucket/collision on the hot code path for each cache access.
>
> Per Minborg has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - Simplify benchmark
> - Add benchmark
test/micro/org/openjdk/bench/java/time/ZoneOffsetBench.java line 66:
> 64: for (int s : CACHED_SECONDS) {
> 65: ZoneOffset zo = ZoneOffset.ofTotalSeconds(s);
> 66: sum += zo.getTotalSeconds();
I think we should feed the value of `zo.getTotalSeconds()` into Blackhole, see
https://github.com/openjdk/jmh/blob/master/jmh-samples/src/main/java/org/openjdk/jmh/samples/JMHSample_34_SafeLooping.java#L128
-------------
PR: https://git.openjdk.org/jdk/pull/12346
